LCD TV Question

[sherlock]

Hello to all,   I've seen that several people here have had some success repairing older LCD TVs...  I was recently given a non-working APEX LD3288M TV.  No picture, sound, or anything else.  Standby light is out.  The power supply seems to be functioning normally.  The voltages are correct compared to the labels on the circuit board.  The TV is constantly on, meaning you can't turn it off except by pulling the plug.  The sensing line that controls the power supply from the processor (?) is always "on".  If I disconnect that line the power supply powers down and only the standby 5 V is present.  There's evidence that the main processor has overheated so I'm convinced that the main board is defective.   I've seen several used replacement boards on eBay that look identical to the board I have.  The only difference is on the printed stick-on label with the part number.  Each of the sites selling these boards boards states that you MUST match up the TV model number AND part number of the board might not work.   Herein lies my question....  As the boards are electrically identical (based on the pictures shown, all components, PCB markings, and connectors are exactly like my board), will any one of them work on my TV?  Now I have seen some variations in boards between the same model number and I imagine the warnings are for people that aren't experienced with this type of repair and would order a board based upon the model number solely.  Does anyone in this knowledgeable group know what differences there are between these seemly identical boards?  Is it software related?  Would an identical board from a 40" TV work in my 32" one?  Any help would be greatly appreciated.   Thanks!!   

[superrdan]

Disclaimer, not familiar with this board or tv.

Are the replacement board PCB and your PCB marked with the same numbers and revision?

The stick on label part number, does that match the PCB number or do they use some other number there?

[GreyWoolfe]

Going back to my days of DELL warranty repair work, laptop LCD panels were not necessarily the same and had different inverter boards with different part numbers.  Just because they look the same, they may not necessarily be the same, unless you see both sides of the board and can verify each and every component, including passives, preferably with test equipment.  Even then, they may not be with inner board layers doing different things.  Personally, I wouldn't chance trying it, you could possibly damage the panel.  If the sellers say you must match, then you probably should match.  They are covering themselves from someone performing a repair willy nilly, not knowing what they are doing and then blaming the seller for their mistakes.  Looking up the brand, it seems to be a low end TV and may not be worth the effort or money to fix.

[Brumby]

Going back to my days of DELL warranty repair work, laptop LCD panels were not necessarily the same and had different inverter boards with different part numbers.  Just because they look the same, they may not necessarily be the same, unless you see both sides of the board and can verify each and every component, including passives, preferably with test equipment.  Even then, they may not be with inner board layers doing different things.  Personally, I wouldn't chance trying it, you could possibly damage the panel.  If the sellers say you must match, then you probably should match.  They are covering themselves from someone performing a repair willy nilly, not knowing what they are doing and then blaming the seller for their mistakes.  Looking up the brand, it seems to be a low end TV and may not be worth the effort or money to fix.

Agreed.

Unless you've got the experience to be able to identify compatible boards (and photos of boards that look the same is NOT enough), then err on the side of caution.

[Shock]

You need to match the model and best to match the exact board part number and revision. However some brands use the same part and revision board interchangeably between series and during model refreshes.

Another catch is occasionally some boards need to have firmware replacements, updates, chip swaps or replacements. So make sure you research the model as best as you can prior to taking the plunge (get the service manual if you can find it) and also keep your old board just in case.

Buying secondhand boards can also be hit and miss if it was pulled from a non working TV.

[sherlock]

Thanks for the insight.  From the pictures on eBay the boards have exactly the same markings.  It's not a very complicated board.  The difference is in the stick-on label.  The numbers don't match, although some of them are close.  I'm guessing it could refer to a firmware change or something similar, or maybe a production run marking.  There seems to be a lot of number variations to the same board for the same model TV and other models that use it.  It is a low end TV so yes, it's not worth a lot to try to fix it, but since it was free, a $20-30 investment might be worth it.  I just don't want to waste the money if I definitely need to match the numbers.  That almost seems like a needle in a haystack possibility, given the variations I've seen.  Service manual for it is non-existent as far as I've been able to determine.  Most of the boards advertised claim to come from TVs that are working but have cracked screens but of course there's no way to verify that.  I'll keep looking at the eBay offerings for a while but if anyone has more information, please post it.  BTW I'm experienced in electronic repair and have a good amount of test equipment at my disposal.  And I know how to use it.  :-)